Why sometimes the leaves of deciduous plants do not fall off even in winter?

The leaves of deciduous plants sometimes do not fall in winter because these plants are calorie-starved.
The leaves turn black, but still continue to hang on the branch for a long time. Such plants need feeding. Potassium sulfate is the best vitamin for trees, and if you feed the plants with it in the spring, then everything will return to normal. In the summer, if possible, you can process the leaves with potassium permanganate.